Yes it is more difficult than in say the US but not that hard. You just must document over a period of months that the employee is underperforming and not improving; you can’t just fire them with no notice or warning. Most big corporations in the US work this way anyway as well.
And of course the documentation must include signs that they have been given any required to improve etc.
Depending on how bad it is, the deal settled with the employer will vary. If there is video of an employee sleeping on the job at the factory on severeal occasions, they will probably be let go without compensation. If the employee just complains that a worker is only half as fast as the guy next to him, there is no way the employer can let the guy go without compensation.
You have to consider that for society it is very wasteful to have people live off welfare schemes rather than working. Even if you are not a high performance worker, it is better for society that you are working than staying unemployed.